There is a motion compensated prediction as one of techniques used for encoding a video image.
In the motion compensated prediction, a video encoding apparatus acquires a motion vector using a to-be-encoded image to be newly encoded and a local decoded image already generated and generates a prediction image by carrying out motion compensation using this motion vector.
As one of methods for acquiring a motion vector in the motion compensated prediction, there is a direct mode for generating a prediction image using a motion vector of a to-be-encoded block derived from the motion vector of an encoded block (refer to Japanese Patent No. 4020789 and U.S. Pat. No. 7,233,621). Because the motion vector is not encoded in the direct mode, the number of encoded bits of the motion vector information can be reduced. The direct mode is employed in H.264/AVC.